1. Field of the Invention
The present invention relates to an apparatus and a method for using an expansion key in a portable terminal, and more particularly, to an apparatus and a method for using an expansion key by use of a general purpose input/output (GPIO) extension in a portable terminal.
2. Description of the Related Art
As a portable terminal is included with the main functions of the computer such as word processing, e-mails, chats, or memos, more function keys are required to be incorporated into the portable terminal to use these functions. Devices such as Personal Digital Assistants (PDA) or QWERTY phones, which operate to provide mainly email services or messenger services, particularly need more keys. The keys generally correspond to N columns and M rows of an N*M matrix. For example, up to 25 keys can be provided for a keypad of 5*5 key matrix.
FIG. 1 is a block diagram of a 5*6 key matrix keypad input apparatus of a conventional portable terminal.
Referring to FIG. 1, a keypad of a conventional portable terminal generally includes a Mobile Station Modem (MSM) chip 100 which processes interrupts according to the key input through a key matrix unit 102 of 5 columns and 6 rows, and the key matrix unit 102 which forms a key matrix connected with KEYSENSE pins of the MSM chip 100 so that various numerals or text information, including English or Korean symbols, or the like, can be input therethrough.
For example, the columns of the key matrix unit 102 are in a pull-up state, that is, in a high state, and the rows of the key matrix unit 102 are in a pull-down state, that is, in a low state. If a user presses numeral key ‘1’, KEY SEND8 of the MSM chip 100 is connected with KEY SEND0 such that the voltage level of KEY SEND8 is grounded, causing an interrupt. Accordingly, the MSM chip 100 recognizes the interrupt, conducts key scan and recognizes a corresponding key.
FIG. 2 is a block diagram of an apparatus having an expansion key, which uses a spare External Interrupt port of a MSM chip according to a prior art technology.
Referring to FIG. 2, an expansion key input apparatus of a portable terminal includes a Mobile Station Modem (MSM) chip 200 which processes the interrupt according to the key input through a key matrix unit 204, and which processes data associated with the input of an expansion key from a spare External Interrupt port, and a key expansion unit 202 which generates an interrupt of the expansion key. The key expansion unit 202 is connected between the spare External Interrupt port of the MSM chip 200 and the key matrix unit 204 which forms a key matrix connected with KEYSENSE pins of the MSM chip 200 such that various numerals and/or text information, including English or Korean symbols, or the like, and other various functional information can be input there through.
Conventionally, a key map is configured using 5*5, or 6*6 fixed key matrix which is generally supported by the MSM chip. However, this limits the use of keys due to limited number of the pins supporting the key matrix in one MSM chip, and is disadvantageous for the devices like the Personal Digital Assistants (PDA) or QWERTY phones, which require frequent key inputs. Therefore, it is not only inconvenient, but also time-consuming for a user, because he has to change between different language versions such as English mode, Korean mode, or Number mode while he writes an email or uses a messenger service, due to limited size of the key matrix of the keypad.
A few more keys can be added using a spare External Interrupt port of the MSM chip 200. However, because only a small number of External Interrupt ports is usually provided, a sufficient key expansion cannot be obtained. A custom integrated circuit may also be used to expand the key matrix and provide an increased number of key inputs, but unit cost increases.
Accordingly, an apparatus and a method for a key input of a portable terminal, which use an economic general purpose input/output (GPIO) expansion chip, rather than a custom integrated circuit, to expand input/output (I/O) ports of a MSM chip, and which realize an expansion key matrix by use of the I/O expansion port, are necessary.